1. Field of the Invention
The present invention discloses a controlling circuit for an analog measurement module and a controlling module thereof, and more particularly, to a controlling circuit of isolating noises with the aid of a photo-coupler and of providing a required operating voltage level difference with the aid of a general purpose amplifier and a controlling module including at least one said controlling circuit.
2. Description of the Prior Art
Please refer to FIG. 1, which illustrates a conventional logic tester 110 and an analog measurement module 120 in cooperation with the logic tester 110 for audio measurement. As shown in FIG. 1, the logic tester 110 outputs a control signal to the analog measurement module 120 for measurement and test of AC small signals. The analog measurement module 120 is conventionally provided with a low-noise power, so as to reduce noise coupling from an external power. Since the analog measurement module is often required to test audio signals having different levels of magnitudes, the control signal from a single I/O port of the logic tester 110 is also required to be amplified in its magnitude with different gains, so as to retrieve audio signals having qualified magnitudes for testing. The analog measurement module 120 includes a relay, which is not illustrated herein for brevity, for serving as a switch for selecting amplifiers having different gains. The relay is capable of switching amplifiers having different gains according to a voltage level difference between an input control signal and a DC voltage source, so as to meeting requirements of audio signals having different ranges of magnitudes. The analog measurement module 120 is coupled to an analog ground AGND, and the logic tester 110 is coupled to a DC ground DGND. However, in considerations of various requirements of the analog measurement module 120 in its specifications, the requirements cannot be met by the logic tester 110 since said logic tester 110 can merely transmit control signals with a single I/O port. Besides, the control signal may be coupled to an analog measurement module 120 having unmatched specifications so that noises are introduced; and as a result, measurements of the analog measurement module 120 may be unstable or getting larger so that errors and higher fabrication capitals are both introduced.